The preparation of ethylene glycol-functionalized polycarboxyphenylisocyanides via peptide bound formation has been described by Y. Hase, Y. Mitsutsuji, M. Ishikawa, K. Maeda, K. Okoshi, and E. Yashima, Chem.-Asian J. 2007, 2:755-763. This publication discloses the post-functionalization of water-soluble poly(carboxyphenylisocyanide) according to Formula 1 in dimethyl sulfoxide via a classical peptide coupling strategy. In this case, the materials used were preformed polymers (Mn=3.3×104 g/mol, Mn/Mw=3.2) that were modified after completion of polymerization with different side chains, including cyclic and linear ethylene glycol substituents.
This method does not lead to quantitative grafting of the substituents. Several treatments with the desired amino(ethylene glycol) derivative had to be conducted on the starting materials to lead to an acceptable grafting density of ethylene glycol chains onto the polymer backbone.

Another disclosure of an oligo(ethylene glycol)-functionalized poly (isocyanopeptide) has been published by H. J. Kitto et al., J. Mater. Chem. 2008, 18:5615-5624.
The oligo(ethylene glycol)-functionalized poly(isocyanodipeptide), according to formula 2, was prepared via a post-modification or grafting of ethylene glycol chains making use of a copper(I) catalyzed [2+3] Huisgen dipolar cycloaddition between acetylenes and azides. Acetylene-functionalized poly(isocyanodipeptide)s were first prepared and further modified by 13-azido-2,5,8,11-tetraoxatridecane, resulting in hydrophilic to fully water-soluble materials, depending on the ratio of ethylene glycol chains grafted onto the backbone of the polymer.

This method, however, suffers from several drawbacks with regard to the preparation of biocompatible high molecular weight materials. Due to the inherent low solubility of the starting material (fully acetylene-substituted polymers) and its high tendency to aggregate, polymers with a limited degree of polymerization ([DP] <1200) and a specific type of chirality (LL or DD enantiomers of the dialanine fragments) could be efficiently processed and functionalized.
Like any other type of post-modification strategy, this method inherently leads to polymers more prone to structural defects. For instance, structural defects can be non-reacted acetylene groups within the prepared materials. These might lead to uncontrollable side reactions during further processing of the material, which is undesired.
A still further disadvantage is that the complete removal of copper salts, required for the described click strategy, is difficult due to the complexation ability of oligo(ethylene glycol)s toward cationic species. The removal of copper salts is a prerequisite for any biological application of the material, especially considering the stoichiometric amount of copper used to promote an efficient grafting reaction in the described procedure. This method is, therefore, less suited if the poly(isocyanopeptide)s are to be used in a biological application.
Moreover, the dipolar cycloaddition of alkynes and azides inherently leads to the formation of triazole fragments. In the case of the described polymer post-modification strategy, it results in the introduction of a high density of triazole units onto the polymer backbone that further hinder the complete removal of copper salts from the materials. Indeed, polytriazoles are known to coordinate transition metals cations and are specifically used as ligands for copper.
Moreover, triazoles are prone to ionization under physiological conditions, which can lead to unwanted ionized species such as polyelectrolytes.